


First Time

by withtheworms



Category: Undertale (Video Game)
Genre: Blow Jobs, Bonsai AU, First Time, Frottage, Hand Jobs, M/M, PWP, Vaginal Fingering, consent and feelings, cute sappy domestic, skeleton magic AND fire magic, the gang's all here, together at last
Language: English
Status: Completed
Published: 2019-05-25
Updated: 2019-05-25
Packaged: 2020-03-17 08:41:00
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,071
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18961768
Author URL: https://archiveofourown.org/users/withtheworms/pseuds/withtheworms
Summary: Bonsai AU.  Sans comes home from work to a surprise date night from Grillby and it's cute and domestic and then fuckin' happens.  Except Sans hasn't done any of this before so everyone has to have Feelings about it.Lots of flexibility about what skeleton AND fire magic can do.  I cannot stress enough how this is all about consent and feelings.





	First Time

**Author's Note:**

> So it's been a hot minute- I never really went away I just haven't had capacity to write a single word for awhile. If you don't know our most precious Bonsai AU that Sekrit and I made up, in a nutshell: it's a Sans and Grillby swap. Sans runs the bar and Grillby is his regular. Hijinks ensue. (It's mostly about soft sappy feelings. Not a sad AU.) This is based far enough along in the AU that Grillby and Sans are living together but not for long enough that they've realized they're each others' forever-evers. 
> 
> I like this ship so much and I love this AU forever, sorry it's so stable and sappy hahahha please don't judge me.

Sans hadn’t read that the forecast was calling for snow.  

The presence of it didn’t surprise him as much as the sheer _volume_ of it _;_ thick fat flakes globbing together in clusters that were falling heavy and creating a fresh blanket of white.  The sight of it all cowed him as he stood outside the door to the bar, locking up before he paused to readjust the collar of his jacket, pulling it as high over his skull as he could and wishing that he’d brought a hat.  The worst thing about walking home in the snow was the way the flakes fell at just the right angle to drift into his eye sockets. It was unpleasant, to say the least, and the cold slide of melting slush pooling in the back of his skull made him shudder as he hunched himself against the elements and began the trudge home.  

It wasn’t far.  Just a couple blocks between the bar and home.  He remembered the days when he used to walk back to a cold, dark house, exhausted from a day of work, doing his best to make himself eat something before he slumped dreamlessly into bed.

Things were so much different, now.  

The lights inside the house were on, casting a warm glow onto the snow as he approached the front steps.  The walk had been shoveled, but he noticed the effort had been made several hours ago, leaving a fuzzing of soft powder for him to track inside as he opened the front door.

It was warm.  It was always so warm, now.  Sans felt something in him that he hadn’t realized was coiled relax automatically, the heat- Grillby’s heat- wrapping around him like an embrace he could dissolve into.  

“I’m home.”

Sans was hanging up his jacket when he felt Grillby’s arm curl around him from behind, warm and comforting and _large._  He allowed himself to lean back into his heat before he turned and was met with a gentle but affectionate kiss.

“Welcome home, Sans.”

Sans still wasn’t sure what to make of this.  The open, unabashed affection, the stable domesticity, the comfort of someone waiting for him when he got home. It was nice.  It was _so_ nice.  But a part of him still had to force himself to enjoy it– to _believe_ it.  Grillby was here, and he was… _they_ were, for now, happy.

“Busy day?”

“Mm,” Sans allowed himself to lean into Grillby’s touch for a moment longer. “Yeah.  Happy to be home.”

Grillby kissed the top of Sans’s skull before he detangled himself and returned to the kitchen.

“Well get settled.  Dinner’s almost ready.”

“Dinner?” Sans asked, following after him.

“Dinner,” Grillby repeated, resuming tending what he’d left simmering on the stove. “Date night.”

Date night.  Sans blushed despite himself.  It was a nice concept, but it still made him feel silly.  He didn’t deserve this fussing, and Grillby _insisted_ on fussing.  

"Sit down, I’ll get us some wine started.”

"Wine? What’s the occasion.”

Grillby cocked an eyebrow, and Sans felt the warm, unabashed affection radiating off of him. “The occasion is that I like to take care of you.”

Sans grinned, relenting at last.  It was easy, really, to nestle into the comfort of Grilby’s attention and affection.  It was easy to let Grillby take care of him, to welcome him home and serve him dinner.  It was easy to move to the couch after they’d eaten and the plates had be cleared away, Grillby listening as Sans recounted his day, highlighting the news and gossip from each of the bar’s regulars.  

It was easy for Grillby to move a little closer every time he laughed.  

It was easy for his hand to rest warm and casual on Sans’s leg.

And it was easy– so easy– when he leaned forward mid-anecdote and kissed Sans.

Sans hummed and allowed the kiss to happen, but leaned back after a moment, a flicker of uncertainty in the corner of his grin.

"What’s the occasion for that?”

Grillby smiled patiently and kissed Sans again, slow and leisurely.

"The occasion is I like to kiss you.”

Sans managed a small laugh against Grillby’s lips, forgetting the rest of his story as he leaned to pursue another kiss.

"Maybe the occasion is I like to be kissed by you, too...”

The shift was subtle but palpable.  Suddenly Grillby’s hand wasn’t just idly resting but actively seeking, sliding up above his knee as he leaned forward, using his other hand to angle Sans’s skull just slightly.

"Grill–” Sans’s words were cut off as Grillby kissed him again, gentle but firm, the warm hand on his skull sliding along his jaw bone, encouraging him to part his teeth as Grillby’s hot tongue slid into his mouth, tasting him deeply.

They parted after a moment, foreheads touching as they rested against one another.  Sans’s eyes were soft, the blush spread across his face nearly consuming his entire skull. Grillby’s hand gently stroked his cheek as he inclined his head for another kiss, speaking softly as his lips brushed against Sans’s jaw.

"Is this okay?”

Sans felt Grillby’s other hand- a warm pressure near his hip- press gently on his leg, massaging soft circles into his thigh.  He closed his eyes, acknowledging the heat pooling within him, nervous and unsteady but _wanting_ , and nodded his head minutely, allowing himself to be lead as Grillby pulled him into another kiss- deeper this time.  Hungry.

"I want you…” Grillby’s words were a soft rumble, his kisses drifting from Sans’s mouth and down his neck, breath hot against his vertebrae. “Please…”

Sans could feel Grillby’s arm curl around him, the hand on his leg moving, running soft and warm over his stomach and the obvious fat of his belly, and pressing gentle but insistent against his collected magic.  At that touch the warmth he was feeling twisted immediately into something sharp and self-conscious, and he longed to pull away and collect his thoughts. However, Grillby had anticipated this, the arm around him tightening as Sans felt himself drawn closer to his solid, fiery form.

"You’re so hot, Sans…”

"Nn…”

The sound was out of Sans before he could prevent it, and any argument was stymied by Grillby’s insistent press and the push of his tongue invading Sans’s mouth again, delving deeper, so that Sans was instinctively inclined to summon his own tongue to press back.  

He couldn’t remember how he ended up on his back, reclined on the couch with Grillby resting comfortably between his legs.  He felt the weight of Grillby’s body pressing down on his, and the sharp jolt at the first experimental grind of Grillby thrusting once against him, accompanied by the slow crawl of Grillby’s hand towards his belt.  

They’d gone this far before.  The heated exchange of kisses and escalating pressure of bodies rocking gently against one another; the warmth through clothes and the throb of magic.  However, every time, the heat of the moment had opened that deep well of inexperience within Sans, and he felt what he lacked acutely, his insecurity creating an impassable threshold for him.

"G… Grillby…” Sans moved, groping for Grillby’s hand, which had begun rubbing lower on his stomach as he inched up Sans’s shirt and tracked towards his crotch. “Hang on.  S… slow down.”

“I’ll go slow,” Grillby’s voice was a sultry rumble under the soft crackle of his flames, and Sans felt his pulse jump at the lidded look the fire monster was giving him.  There was so much confidence there, so much _experience_.  Grillby’s hand continued to wander lower, the pad of his thumb rubbing slow circles over Sans’s crotch.  

Sans’s anxiety peaked.

“I can’t.” It was out of him before he could think it through, and the freezing of Grillby’s touch was immediate.  With a shift Grillby was off him, injury and frustration evident on his face only for a moment as he struggled to get himself back in order.

Sans propped himself up, awkward and uncomfortable, fumbling to smooth his shirt back down.

Silence yawned between them.

“I’m sorry,” Grillby said at last, looking down at his hands as if he’d done something wrong.

“It’s not your fault,” Sans replied, sounding lame and painfully aware of it.

“Am... I missing something?” Grillby wasn’t accusing, but Sans felt it innately. “You act like you want me, but... if you don’t _want_ this, and if I’m making you uncomfortable...” Grillby was skirting around something _much_ more complicated, and the idea that he was starting to worry about Sans’s willing participation sent a jolt of panic through the skeleton.

“Grillby.” Sans’s hand was on Grillby’s shoulder without a second thought, his touch firm but gentle as he sought to quell the mounting discomfort in the air. “That’s not it.  That’s not it at _all_.  I… I want you, Grillby.” The confession hung raw between them, and Sans struggled to control his blush at the openness of his phrasing.

“Then… what’s the problem?” Sans could see Grillby doing the math, trying to find the hidden obstacle. “I want you, too, Sans.  I want _all_ of you.  I know I can make you feel good.  I'm not gonna disappear in the morning.  Please... just give me a chance.”

“It’s not that…” Sans wanted to look anywhere else but forced himself to maintain eye contact, feeling a tremor in his touch as Grillby’s hand raised to rest on his wrist. “It’s not you.  It’s… it’s me.” The words escaped him in a huff, his shoulders sagging with the weight of it. “I haven’t… I’ve never done this before. Not with- well, anybody.”

He held his breath, waiting for the inevitable scoff and incredulity.  

Instead, he felt the slow drift of Grillby’s hand as it moved from resting on Sans’s wrist to traveling up his arm.

“I’m sorry,” Sans mumbled. “I know that’s hilarious and embarrassing.”

“Sans,” Grillby’s voice was soft and not remotely condescending, and Sans fell into his touch almost instinctively as he drew his body closer. “Look at me.”

Sans looked up and barely had time to react as Grillby lifted his glasses off his skull, folding them before he set them next to the forgotten wine on the table.

His touch returned; warm and gentle but strong, stroking the side of Sans’s face.

“Sans.  Can I be your first?”

The strangled little noise that escaped Sans was almost comical, but Grillby didn’t laugh, instead reaching with his free hand to weave his fingers with Sans’s, gently rubbing his thumb across his knuckles.

“You can say no.  I won’t be offended.  I know it’s a lot to ask-”

“Grillby.” Grillby stopped and the skeleton smiled, leaning forward as he pressed a gentle, seeking kiss to his lips. “You just have to show me how it goes.”

The smile that overtook Grillby’s face was radiant, and he leaned into Sans’s kiss eagerly, pushing him back again as he sank the smaller skeleton down into the cushions of the couch.

“Do you want it here?” his kisses were muffled into the crook of Sans’s neck, and the skeleton squirmed, gasping out a breath as his hands moved to grip at Grillby’s shoulders. “We can go upstairs…”

“We can start here,” Sans was quiet but coy with his words, and Grillby felt the heat within him spike.

“I’m gonna take your shirt off, okay?” Grillby’s hands dipped under the bottom of Sans’s shirt, but he waited for the small breath and sharp nod from the skeleton before he began to ease it up over his head.  The exposure of bare ribs and the soft glow of his magic in the swell of his stomach made Grillby ache, and his mouth moved quickly as he began exploring the skeleton’s body.

For his part Sans remained quiet, breath coming in soft pants as he felt Grillby’s kisses travel lower, a soft moan wrenched from him as a warm tongue slipped out to explore his stomach.

“Grillby…”

“I love this,” Grillby mumbled, nuzzling the swell of his magic. “I love the shape of you.  God, you’re so hot.”

Sans felt more than saw the hands starting to loosen his pants and he groaned, the sound small and anxious as he struggled to prop himself up.

“H… hang on.”

Grillby’s hands stopped and he looked up, his expression patient as Sans attempted to find the right words.

“I don’t want to disappoint you,” Sans finally managed, somewhat lamely. “I know... I’m going to be bad at this.”

Grillby smiled, warmth and deep affection laden in the expression.

“Nothing with you has ever been bad,” he soothed, pressing another kiss to Sans’s stomach. “Please, just let me see you.  We don’t have to go any further than that if you don’t want to.”

Sans hesitated, but after a pause began to move, helping Grillby as he finished undoing his pants, sliding them off his skeletal hips, revealing the magic collected loosely in the cradle of his pelvis.

“I’ve never been with a skeleton before,” Grillby mumbled, head still level with Sans’s stomach as he studied the blue shifting of his magic.

“Yeah,” Sans huffed, grinning weakly. “There’s not many of us to go ‘round.”

“Is this… what it’s supposed to look like?”

Sans couldn’t help his smile, running the finger of his hand through the flames of Grillby’s hair.

“No, it’s just… ah.  We’re just getting started.” He pulled gently, trying to ease Grillby up. “Come here and kiss me.  You’ll see.”

Grillby obeyed, moving up Sans’s body as he met him with a kiss, mouth open, heat invading as he pressed against Sans’s tongue, his hand continuing to rove across his ribs and belly.  This wasn’t the first time Sans had shaped something with his magic, but it was the first time he’d done it with another body present. The usual fantasies replaced by the real thing helped Sans along easily, and it didn’t take long before his magic solidified, the press of his erection immediately noticed by Grillby, who parted from Sans’s kiss, panting as he grinned down at him.

“Oh.”

“Yeah…” Sans smiled nervously as Grillby leaned back, gazing at Sans as he took in the new shape of him. “I guess, uh… ta da?”

Grillby’s hand moved unbidden, but he hesitated and gave Sans a seeking look.

“Is it okay if I…?”

“Grillby.” Sans smiled, weak with want as he gazed up at the fire monster crouched in front of him, admiring the broad curve of his shoulders and the obvious but non-invasive press of his thigh between Sans’s legs. “ _Please_.”

The feeling of Grillby’s fingers curling, warm and tender around his length was indescribable.  Sans drew in a deep breath and closed his eyes for a moment, enjoying the sensation before he forced himself to open them and watched, mesmerized, as Grillby began to stroke him.  

“Grillby…”

“Yeah…” Grillby leaned forward, his free arm curling around Sans’s middle to pull his body closer as his hand continued working Sans, taking his time as he began to build the skeleton up.

Sans was struggling to absorb all that was happening, Grillby’s kisses momentarily commanding his attention while his hips thrust in uncoordinated movements up into Grillby’s hand.

“That feels…” Sans trailed off as he held tight to the material of Grillby’s shirt, pressing his forehead into his chest.

“Yeah?” Grillby’s voice was low and heated, panting as he curled over Sans, weakly grinding himself against Sans’s thigh as his hand began to speed up. “How does it feel?”

“Gh…. oh my god,” Sans’s forehead pressed more insistently into Grillby’s chest, and his hips gave a sharp thrust upwards, fucking into Grillby’s warm touch. “Fff...feels so good.”

Grillby grinned and twisted his hand, wrenching a desperate noise from Sans. “I love the noises you’re making.” He hesitated, rubbing his other hand along the side of Sans’s ribs as he continued to stroke him. “I want to put my mouth on you.  Is that okay?”

Sans was breathing quickly and could only nod, fingers curling into the flames on Grillby’s head as the fire monster lowered himself, kissing across his stomach until all at once Sans felt the enveloping heat of Grillby’s mouth as he took the head of his cock into his mouth.  Sans didn’t make a noise, gritting his teeth as his hips thrust up desperately into the slick warmth. Grillby allowed himself to be used for a moment before he gently pressed a hand against Sans’s hips, slipping his mouth off him as he trailed his tongue down his length.

“I like this, Sans,” he mumbled, cradling Sans’s dick against his face. “I like you...”

Without waiting he drew Sans back into his mouth, bobbing his head as he moved his tongue over him, sucking on his sensitive head and overwhelming him to a point that the tension in Sans’s body was so taut it became painful.

“Grillby- Grillby _please_ !” Sans’s fingers twisted suddenly, pulling tight at Grillby’s flames as he squirmed beneath him. “T- too much- please _please_.  I n… need a break.”

Grillby was off him instantly and without question, smiling understandingly and wiping his mouth with the back of his hand before moving himself back up Sans’s body, nuzzling against him as the skeleton caught his breath.

“That was good, Sans.”

“Mmn…” Sans nuzzled into the crook of Grillby’s neck, still breathing hard and embarrassed. “I’m sorry… I got overwhelmed.  I’m bad at this.”

“Don’t apologize,” Grillby comforted. “Would you like to try something else?”

“Mm,” Sans  mused, his hand hovering hesitantly around Grillby’s waist as he considered the offer. “I’d like to get you out of these clothes.”

Without a second of hesitation Grillby sat up, resting on bended knees as he pulled his shirt off over his head, exposing the broad expanse of his chest and the tight flames that formed his torso.

“God,” Sans hissed, almost overwhelmed at the sight of him. “You’re hot.”

Grillby grinned, leaning over Sans to press another kiss on him as he undid his belt.  Sans’s hands touched the bare flames of his chest hesitantly at first, but with increasing confidence as Grillby finally managed to get his own fly undone.

“We can make it hotter…”

Grillby slid his pants down, Sans breaking their kiss to almost unabashedly observe, and the skeleton found that he was… surprised.

“Is that…?”

“It’s what I prefer,” Grillby explained simply, his tone low and without defensiveness.  

Sans nodded, his touch trailing lightly down Grillby’s abdomen. “I can make mine like that, too,” he explained, almost conversationally, fingers pausing the lower they got on Grillby’s stomach. “I mean…” he paused, blushing. “I _haven’t_ , but… I know I can.”

Grillby grinned, filing that information away, his hand covering Sans’s as he encouraged his touch to dip lower. “I’ll change it, just… first, I want to feel you…” He bit his lip, strangling a hiss as he guided Sans’s fingers between the cleft in his core, groaning as Sans’s touch dragged over his clit and slipped into his wet warmth. “Oh god… Sans…”

He tipped his head forward, resting it in the crook of Sans’s neck, his hips rocking gently as he coaxed Sans’s fingers further into him, his large hand enveloping the thin bones of the skeleton as he guided his touch, rubbing himself in a way that pulled small, needy noises from his own throat.  

They continued, so that soon Grillby was pressed flush against Sans as Sans worked his fingers in and out of him.  The press of Sans’s erection remained between them, and at a point Sans groaned as his hips gave an involuntary jerk upwards. “Grillby… d… do you want me to….?”

“No, no,” Grillby panted, slowing Sans’s hand as he began to come back into himself. “I mean… yes, maybe.  One day. If… if that’s what you want. But for today, I…” Gingerly he removed Sans’s hand, and in a moment of concentration his fire began to reshape itself, forming into a hard length before Sans could question it.

“I want our first time to be like this,” Grillby explained as he lowered himself again, pressing a kiss to Sans’s mouth.  His hand returned to San’s length, stroking him slowly, and with only a moment of hesitation he felt Sans’s slick fingers wrap around his cock and begin to pull.

Their movements continued with a steady escalation until both their hands were moving quickly, sharp gasps and panting breaths filling the room.

“Sans…” Grillby was breathing hard and beginning to come undone.  He knew Sans would have at least some experience in this area, but he hadn’t anticipated how incredible it’d feel just to have his touch wrapped around him. “This is so good…”

“I’ve been fantasizing about you since you moved in,” Sans confessed, hushed and gasping as he thrust up into Grillby’s hand. “God.  Grillby– f-fuck. I want you.”

“Yeah?”

Sans nodded, moaning as Grillby lined up their erections and thrust against him hard. “Yes, like that.  Oh god, Gr...illby, please…”

Grillby set a rhythm, moving against Sans until the skeleton was canting his hips up to meet him.  Without hesitating Grillby shifted his hand, gripping both their lengths and stroking them in tandem, his hand forming a ring of heat that caused Sans to make a noise that almost made Grillby come undone.

“Do you want me inside you?” The question was panted roughly against Sans’s ear as he continued to fuck him into the couch.

“N… next time,” Sans gasped, fingers digging into Grillby’s shoulders, his voice breaking into another desperate moan as he thrust up into Grillby’s heat. “I’m so close– I’m, _fuck_. Grillby…”

Sans’s voice was almost pleading, and Grillby groaned, low and wanting as his movements sped up against Sans, urging the skeleton on.

"It’s okay,” he soothed. “I’ve got you.  You’re doing so good....”

Something in his words struck Sans, and his body locked up beneath Grillby, a strangled sound escaping him as he jerked and came hard into Grillby’s palm.  His cum hissed as it came into contact with Grillby’s flames, and Grillby made a soothing noise as he continued stroking him through his aftershocks, encouraging him as he kissed into the crook of his neck.  

He waited patiently until Sans finally sagged back down into the couch before he released the skeleton’s spent cock, propping himself up slightly and rapidly moving his release-stained hand over his own length, bucking into his grip until he finally came messily across Sans’s softening magic, grunting as he stroked himself through his orgasm before pressing an uncoordinated kiss to Sans, who hummed sleepily into the gesture.

The urge to let his elbow buckle and curl up in the mess they’d created presented itself temptingly, but with a not-unhappy sigh Grillby shifted his weight and got to his feet, hesitating with his pants halfway down his legs; momentarily undecided on what to do with them before he shrugged and shucked them off, walking naked into the downstairs bathroom and returning a moment later with a hand towel.  

“Here,” he said, nudging Sans, who had remained laid out comfortably on the couch.  Sans moved his legs just enough for Grillby to sit back down and smiled drowsily as Grillby wiped him off, blushing slightly as the fire monster bent down to kiss his stomach one last time before he tossed the towel aside and tucked himself back up against Sans’s side.

“Hi,” Sans mumbled, curling an arm loose around Grillby.

“Hi,” Grillby replied, cuddling into Sans’s chest.

The afterglow was fading and Sans was slowly starting to come back into himself, his hand idly petting through Grillby’s flames as he shifted on the small area of the couch to draw the larger monster closer to him.

“Grillby,” he squirmed, looking to catch the other monster’s eye before he kissed him, long and gentle.  

Grillby let himself relax into the kiss, arms curling tight around Sans’s significantly smaller frame. Eventually they parted, and Grillby smiled, his head resting comfortably on the skeleton’s chest. “Do you want to go upstairs?”

“Mm…” Sans yawned but shook his head, continuing to pet his hands through Grillby’s flames. “Let’s just stay here for a bit longer.”

Grillby felt a pulse go through him; something deep and rich and happy, and he allowed himself to close his eyes and relax. “Okay,” he murmured. “I’d like that.”


End file.
